Grinding apparatus for vegetable materials

ABSTRACT

The invention relates to a grinding apparatus for vegetable material which is disintegrated in an interspace between the opposed grinding surfaces of two grinding discs mounted rotatably in relation to one another within a stationary frame. At least one of the grinding discs is carried by a rotatable shaft which in turn is surrounded concentrically by a screw conveyor for the material to be disintegrated in the grinding interspace, which conveyor is driven at a substantially lower rotational speed than the shaft carrying the grinding disc. Disposed between said shaft and the conveyor and between the latter and the stationary frame are stuffing boxes intended to prevent steam from seeping out of the apparatus and particles of grinding produce from penetrating into the space between the shaft and the screw conveyor. These stuffing boxes are supplied with cooling water under pressure from a common source in such a manner that the cooling water first passes through the stuffing box between the frame and the conveyor screw and therefrom to the stuffing box between the conveyor screw and the rotatable shaft.

Muted States Patent [1 1 [111 3,845,909

Johansson Nov. 5, 1974 GRINDING APPARATUS FOR VEGETABLE [57] ABSTRACTMATERIALS The invention relates to a grinding apparatus for vege- [76]Inventor: lnge J. G. .lohansson, Falkvagen 61, table material which isdisintegrated in an interspace 183 50 Taby, Sweden between the opposedgrinding surfaces of two grinding discs mounted rotatably in relation toone another [22] Filed May 1973 within a stationary frame. At least oneof the grinding [21] Appl. N0.: 357,010 discs is carried by a rotatableshaft which in turn is M surrounded concentrically by a screw conveyorfor the 30 F A P D t material to be disintegrated in the grindinginterspace, 1 M fg g ppslcadlon y a a which conveyor is driven at asubstantially lower rotaay 1 we en "6254/72 tional speed than the shaftcarrying the grinding disc.

M Disposed between said shaft and the conveyor and be- C(il. 241/6565?!tween the latter and the Stationary frame are stuffing [58] Field ofsearch 241/66, 65, 67, 247, 250 bxes intended seeping of the apparatusand particles of grinding produce from [56] References Cited penetratinginto thlehspace btettweeli; the shaft and 1th?1 screw conveyor. ese stumg oxes are supp ie UNITED STATES PATENTS with cooling water underpressure from a common 1,719,784 7/1929 ROSS t 241/67 source in uch amanner that the cooling water first 1,937,788 12/1933 Ross 241/66 Xpasses through the Stuffing box between the frame and ii zg 2: 55:11al'm 22 2; the conveyor screw and therefrom to the stuffing box3:467:323 gngg Asplund ct aim 241/247 between the conveyor screw and therotatable shaft. 3,717,309 271 973 Luker et al. 241/247 3 Claims, 2Drawing Figures Primary Examiner-Granville Y. Custer, Jr. AssistantExaminer-Howard N. Goldberg 1 1, l l m i i 9 a 5 i a I l 2 v 8 x T A NGRINDING APPARATUS FOR VEGETABLE MATERIALS BACKGROUND OF THE INVENTIONThe invention relates to a grinding apparatus for vegetable materials ofthe type comprising two grinding discs mounted rotatably in relation toone another within a stationary frame, at least one of said grindingdiscs being carried by a rotatable shaft surrounded con centrically andfreely by a screw conveyor from an inlet opening in the frame to thegrinding surfaces of the discs. This conveyor is driven at a lowernumber of revolutions per minute than said shaft and serves to feedmaterial to the grinding discs. Grinding apparatus of this kind aredisclosed e.g. in the US. Pat. specification No. 3,467,323.

SUMMARY OF THE INVENTION mon external source of pressurized water, suchas a pump, while simultaneously preventing fibrous particles fromentering into the interspace between the shaft and the screw conveyorinspite of the high pressure prevailing in the zone for feeding thematerial to be ground into the grinding interspace between the grindingdiscs. Furthermore, steam is usually supplied to the material to beground when it is fed from a chute to the inlet opening in order tobring about a softening or steaming of the material.

According to a main feature of the invention water is supplied to thestuffing box pressurized between the shaft and the conveyor whichchannels in turn communicate with a stationary supply channel from thepressure water source via the stuffing box located between the frame andthe conveyor screw.

The object of both stuffing boxes is to prevent steam from escaping dueto the over-riding pressure prevailing in the inlet opening and byreason of the over-riding pressure which is produced at the inner sideof the grinding surfaces. These conditions arise also if the dischargeside of the grinding space is under atmospheric pressure.

By supplying water under over-riding pressure continuous flow of waterthrough the space between the shaft and the screw conveyor in adirection towards the grinding discs is ensured so as to preventparticles of grinding produce from penetrating into said space andthereby establishingfrictional contact with the shaft and the conveyor.It will be apparent that such contact would cause wear and increasedpower consumption due to thegreat R.P.M. differential between thegrinding disc shaft and the screw conveyor. The stuffing box between thescrew conveyor and the stationary frame permits a transfer of coolingwater to the channels of the rotating conveyor without requiringparticular sealing devices.

BRIEF DESCRIPTION OF THE DRAWINGS Further objects and advantages of theinvention will become apparent from the following description,considered in connection with the accompanying drawings, which form partof this specification and of which:

FIG. 1 is a lateral view, partially in vertical longitudinal section, ofa portion of a grinding apparatus embodying the features of theinvention.

FIG. 2 is a sectional view on a larger scale of the right hand portionof FIG. 1.

DESCRIPTION OF AN EMBODIMENT OF THE INVENTION outwards from an innerfeeding zone 24. The material to be ground is fed to the zone 24 bymeans of a screw conveyor 26 which is mounted concentrically about theshaft 12 at a spaced distance 28 between the conveyor and the shaft. Theconveyor is provided with a suitably helically shaped worm member 30extending between an inlet opening formed in the stationary frame forthe material to be ground and the zone 24. Usually a hopper (not shown)is disposed over the inlet opening 32 and is kept filled with thematerial to be ground such as wood chips. The screw conveyor 26 may becomposed of a cylindrical tube 34 defining the space 28.

0 The outer end of the tube 34 is rigidly secured to a tubular member 36having a thicker lateral wall. Connected with said tubular member isalso a tapering tubular element 38 merging at its narrower end with thetube 34 and located directly below the opening 32. While the shaft 12may rotate with an R.P.M. of l,800,the R.P.M. of the rotating screwconveyor is substantially less, such as ISO R.P.M. The screw conveyor 26is mounted in bearings at its external end only, e.g., by means of twoball bearings 40 between which a driving member, such as a gear wheel 42is mounted for rotating the conveyor.

Disposed between the shaft 12 and the conveyor 26 is a first stuffingbox generally denoted 44 and between the conveyor and the stationaryframe 10 a second stuffing box generally denoted 46. Both stuffing boxesmay be of the same construction and each may comprise a'series ofsealing rings 48 made of compressible conventional material and spacedfrom one another by a distributor or spacing ring 50 or 51,respectively,

made of some harder material, such as metal. Formed stuffing box 46 isrigidly secured to the frame 10 and cooperates with a cylindricalsealing surface formed on the external side of the tubular member 36,and, if desired, provided with a separate lining 66. In the illustratedembodiment the stuffing box 46 is. supportedby an annular element 68secured to the frame and formed with an annular inner channel 70 whichis supplied with cooling water through a channel 72 from a pressurewater pump (not shown) connected to the frame. The element 68 haschannels 74 equally distributed about the circumference and connectingthe channel 70 with the outer annular groove 54 of the distributor ring.From here the pressure water is distributed on both sides to the sealingrings 48 so as to cool said rings and furthermore to make sure thatsteam which due to the over-riding pressure prevailing in the feedingzone 24 is forced backwards towards the inlet opening 32, is preventedfrom continuing further to the bearings 40 and to the driving member 42for the screw conveyor. The stuffing box 44 is located in radialdirection inside the bearings 40 and therefore, in axial directionoutside the stuffing box 46.

Formed in the annular member 36 of the screw conveyor is a channelsystem 76 which connects the grooves in the distributor ring 50 of thestuffing box 46 with the grooves in the distributor ring 51 of thestuffing box 44 so that said last-mentioned stuffing box also issupplied with cooling water under over-riding pressure. In addition,this cooling water provides a flow of water through the space 28 betweenthe shaft 12 and the screw conveyor 26 so as to prevent said space frombeing clogged by ground produce which would cause considerable wearand/or production of heat and increased consumption of power for therotation of the shaft 12 due to the great R.P.M. differential betweenthe shaft and the conveyor.

According to the invention, cooling water can be fed to the stuffing box44 inspite of the fact that this stuff ing box is positioned between twoparts both of which rotate. The stuffing box 46 also serves the dualpurpose of a sealing transfer device for the cooling water hetween thestationary frame and the stationary pressure water source and therotating screw conveyor.

While a specific embodiment of the invention has been shown anddescribed, it is to be understood that this is for purpose ofillustration only, and that the invention is not to be limited thereby,but its scope is to be determined by the appended claims.

What is claimed is:

1. In a grinding apparatus, for vegetable materials, of the typecomprising two grinding discs mounted rotatably in relation to oneanother within a stationary frame, at least one of said grinding discsbeing carried by a rotatable shaft surrounded concentrically and freelyby a screw conveyor for feeding material to be ground from an inletopening in the frame to the grinding surfaces of the discs, and drivenat a lesser number of revolutions per minute than said shaft; theimprovement which comprises a stuffing box disposed between the shaftand the conveyor laterally of the inlet opening, said stuffing box beingsupplied with water under pressure through channels formed in theconveyor which channels in turn communicate with a stationary feedingchannel from an external pressure water source over a second stuffingbox located between said frame and said conveyor screw.

2. In the apparatus as claimed in claim 1, in which the first-mentionedstuffing box is disposed outside the second-mentioned stufiing boxviewed in axial direction.

3. In an apparatus as claimed in claim 2, in which the bearings forsupporting the screw conveyor.

1. In a grinding apparatus, for vegetable materials, of the typecomprising two grinding discs mounted rotatably in relation to oneanother within a stationary frame, at least one of said grinding discsbeing carried by a rotatable shaft surrounded concentrically and freelyby a screw conveyor for feeding material to be ground from an inletopening in the frame to the grinding surfaces of the discs, and drivenat a lesser number of revolutions per minute than said shaft; theimprovement which comprises a stuffing box disposed between the shaftand the conveyor laterally of the inlet opening, said stuffing box beingsupplied with water under pressure through channels formed in theconveyor which channels in turn communicate with a stationary feedingchannel from an external pressure water source over a second stuffingbox located between said frame and said conveyor screw.
 2. In theapparatus as claimed in claim 1, in which the first-mentioned stuffingbox is disposed outside the second-mentioned stuffing box viewed inaxial direction.
 3. In an apparatus as claimed in claim 2, in which thefirst-mentioned stuffing box is disposed radially inside bearings forsupporting the screw conveyor.